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22 Nov 1993

Volume 63, Issue 21, pp. 2857-2972

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Optical investigation of confinement and strain effects in CdTe/(CdMg)Te quantum wells

B. Kuhn‐Heinrich, W. Ossau, H. Heinke, F. Fischer, T. Litz, A. Waag, and G. Landwehr

Appl. Phys. Lett. 63, 2932 (1993); http://dx.doi.org/10.1063/1.110277 (3 pages) | Cited 31 times

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We present optical investigations on CdTe/(CdMg)Te single quantum wells (QWs) and demonstrate the high structural quality of the pseudomorphic grown QWs structure which shows high photoluminescence efficiency up to room temperature. Due to the large band‐gap difference between CdTe and Cd0.51Mg0.49Te of more than 0.8 eV remarkable strong confinement effects are observable. A strong enhancement of the exciton binding energies is found by decreasing well width. In the 50‐Å‐wide QW the binding energy is more than two times larger compared with that of bulk CdTe. In addition, a strong functional dependence of the localization energy of donor bound excitons on the well thickness is found. A valence‐band offset of 30% in the strain‐free limit is determined from the energy difference between heavy‐ and light‐hole excitons which is consistent with the strong blue shift of exciton energies by decreasing well widths and the observed effective electron‐hole confinement.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Molecular beam epitaxial growth of CdZnS using elemental sources

B. J. Wu, H. Cheng, S. Guha, M. A. Haase, J. M. De Puydt, G. Meis‐Haugen, and J. Qiu

Appl. Phys. Lett. 63, 2935 (1993); http://dx.doi.org/10.1063/1.110278 (3 pages) | Cited 13 times

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We report on the first molecular beam epitaxial (MBE) growth of CdZnS on (100) GaAs substrates using elemental Zn, Cd, and S sources. Single crystal cubic CdZnS layers lattice matched to GaAs have been successfully prepared. The competition in incorporation between Cd and Zn under different sulfur flux conditions is investigated. Under appropriate growth conditions, the Cd1−xZnxS composition is directly related only to the ratio of the group II beam equivalent pressures. The background sulfur in the MBE growth chamber is found to etch the freshly thermally cleaned GaAs substrates and generate high density of pits on the surfaces. Methods to prevent the sulfur etching are also discussed.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

SiGe gate oxide prepared at low‐temperatures in an electron cyclotron resonance plasma

P. W. Li and E. S. Yang

Appl. Phys. Lett. 63, 2938 (1993); http://dx.doi.org/10.1063/1.110790 (3 pages) | Cited 21 times

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SiGe gate oxide prepared at low temperatures (25–400 °C) by electron cyclotron resonance (ECR) plasma is reported. 100–200 Å oxides were grown on Si0.8Ge0.2 substrates by ECR oxidation under different bias conditions. The electrical properties of the ECR grown oxides are strong functions of processing conditions and post‐processing treatments. High frequency (1 MHz) and quasistatic capacitance‐voltage ECR grown oxides’ measurements indicate that device quality gate oxides can be produced by this process; specifically, the fixed charge and interface state densities are comparable to those of ECR grown metal‐oxide‐semiconductor capacitors on silicon with an aluminum gate.
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81.65.-b Surface treatments
85.30.Tv Field effect devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

SiO2/Si(100) interface studied by Al Kα x‐ray and synchrotron radiation photoelectron spectroscopy

Z. H. Lu, M. J. Graham, D. T. Jiang, and K. H. Tan

Appl. Phys. Lett. 63, 2941 (1993); http://dx.doi.org/10.1063/1.110279 (3 pages) | Cited 83 times

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Both synchrotron radiation photoemission spectroscopy (PES) and Al Kα photoelectron spectroscopy (XPS) are used to determine the suboxide distribution at SiO2/Si (100) interfaces. High resolution PES measurements clearly resolved various suboxides with chemical shifts of 0.97, 1.80, and 2.60 eV for Si+1, Si+2, and Si+3, respectively. A total of 9.3×1014 atoms cm−2 of suboxide is found by PES measurements while only 4.2×1014 atoms cm−2 is measured by XPS on the same sample. This discrepancy is neither caused, as previously believed, by a difference in SiO2/Si (100) quality nor by a difference in methodology in data analysis. The possible factors, e.g., electron mean‐free path and photoionization cross section, which contribute to the difference between PES and XPS data, are considered.
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79.60.Jv Interfaces; heterostructures; nanostructures
68.35.Dv Composition, segregation; defects and impurities

Observation of cavity effect on spontaneous emission lifetime in AlGaAs quantum microcavities using continuous tuning of emission wavelength

K. Nishioka, K. Tanaka, T. Nakamura, Y. Lee, and M. Yamanishi

Appl. Phys. Lett. 63, 2944 (1993); http://dx.doi.org/10.1063/1.110280 (3 pages) | Cited 14 times

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Cavity effect on spontaneous emission lifetime has been observed through the continuous tuning of the emission wavelength by quantum confined Stark effect in AlGaAs Fabry–Perot microcavities. The obtained emission wavelength dependence of the exciton lifetime shows that the lifetime increases with the emission wavelength, specifically indicating a sharp increase at the cavity resonant wavelength. This behavior agrees well with the theoretical prediction based on the theoretical model of G. Björk, S. Machida, Y. Yamamoto, and K. Igeta [Phys. Rev. A 44, 669 (1991)]. Furthermore, we have also investigated the emission wavelength dependence of the transfer efficiency and obtained good agreement with the theory.
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78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena
42.50.-p Quantum optics
78.55.Cr III-V semiconductors

Spatial confinement of misfit dislocations at the interface of CdSe/GaAs(111)

M. Grün, C. Klingshirn, A. Rosenauer, J. Zweck, and W. Gebhardt

Appl. Phys. Lett. 63, 2947 (1993); http://dx.doi.org/10.1063/1.110281 (2 pages) | Cited 6 times

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High‐resolution electron microscopy of wurtzite type CdSe epilayers grown on (111) GaAs revealed that interfacial misfit dislocations are perfect 60° dislocations with Burgers vectors parallel to the interface. Glide is therefore limited to the (0001) interface plane and the extension of dislocations into the epilayer is suppressed. Single‐beam bright field imaging shows that the 7% mismatched epilayer is free of a dislocation network in its volume.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Necessity of hydrogen for activation of implanted fluorine in Si/SiO2 structures

V. V. Afanas’ev, J. M. M. de Nijs, and P. Balk

Appl. Phys. Lett. 63, 2949 (1993); http://dx.doi.org/10.1063/1.110282 (3 pages) | Cited 5 times

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The elimination of trapping centers in Al/SiO2/Si structures by means of fluorine ion implantation was studied in oxides with various contents of hydrogen. It was shown that significant reduction in the density of electron and hole traps in the bulk of oxide may be achieved only in the presence of hydrogen in the system (wet oxide, or post‐metallization anneal in a hydrogen containing ambient). Similarly, suppression of the generation of Si/SiO2 interface states by radiation is also observed only in hydrogen containing systems. The results suggest that defect precursors such as weakly bonded hydrogen and strained Si—O bonds are eliminated by the fluorine and that hydrogen is necessary for this elimination. It is proposed that H facilitates the F transport by formation of HF molecules.
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71.55.Ht Other nonmetals
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Yx Interaction between different crystal defects; gettering effect
61.80.Jh Ion radiation effects

New insight into proton‐induced latchup: Experiment and modeling

J. Levinson, A. Akkerman, M. Victoria, M. Hass, D. Ilberg, M. Alurralde, R. Henneck, and Y. Lifshitz

Appl. Phys. Lett. 63, 2952 (1993); http://dx.doi.org/10.1063/1.110283 (3 pages) | Cited 9 times

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A combination of irradiation experiments (using energetic protons and heavy ions) and a theoretical analysis was used, for the first time, to study proton induced single event latchup (SEL) in electronic devices. A significant difference between SEL and single event upset (SEU) was found. For SEU the device sensitivity can be predicted by a model assuming the collection of the majority of the charge carriers generated in the sensitive volume by the nuclear fragments of the (p,Si) reactions. For SEL, the measured sensitivities are much lower than predicted by prompt charge collection. Recombination of charge carriers (generated by the heavier fragments) due to a track electric field reasonably explains the SEL data.
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61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Two‐dimensional electron and hole states at the staggered band line‐up interface of InAlAs/InP

J. Böhrer, A. Krost, D. Bimberg, M. Helm, and G. Bauer

Appl. Phys. Lett. 63, 2955 (1993); http://dx.doi.org/10.1063/1.110284 (3 pages) | Cited 6 times

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Crystallographic and electronic properties of the staggered band line‐up InAlAs/InP interface grown by metal‐organic chemical‐vapor deposition are studied using double crystal x‐ray diffraction, Shubnikov‐de‐Haas (SdH), capacitance‐voltage, and calorimetric absorption experiments. Observation of a large number of Pendellösung oscillations in the x‐ray rocking curves, which can be perfectly modeled using dynamical diffraction theory, demonstrate the high crystallographic quality of the interfaces. A two‐dimensional electron gas (2DEG) with ns∼6×1011 cm−2 is formed at the InP side of the interface by carrier transfer from the unintentionally doped InAlAs. The electronic structure of the interface is derived from self‐consistent band structure calculation including many particle corrections and good agreements are found with experimentally observed subband transitions up to n=4.
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68.55.-a Thin film structure and morphology
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Growth of InP epitaxial layers by rapid thermal low pressure metalorganic chemical vapor deposition, using tertiarybutylphosphine

A. Katz, A. Feingold, N. Moriya, S. Nakahara, C. R. Abernathy, S. J. Pearton, A. El‐Roy, M. Geva, F. A. Baiocchi, L. C. Luther, and E. Lane

Appl. Phys. Lett. 63, 2958 (1993); http://dx.doi.org/10.1063/1.110285 (3 pages) | Cited 1 time

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High‐quality InP layers with low impurity backgrounds have been grown by means of the rapid thermal low pressure metalorganic chemical vapor deposition technique, using tertiarybutylphosphine as the phosphorus source. The films were grown at a P:In ratio of 75 or higher, temperatures between 500 and 525 °C, a pressure of 2 Torr and growth rates as high as 2 nm/s. The undoped films were defect‐free with exhibited featureless morphologies, and minimum backscattering yields (Xmin) as low as 3.1%, measured by ion channeling. The electrical quality of the films (Nd=2.5×1016 cm−3, μ=4200 cm2/V s) was also excellent.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Energy‐resolving superconducting x‐ray detectors with charge amplification due to multiple quasiparticle tunneling

C. A. Mears, Simon E. Labov, and A. T. Barfknecht

Appl. Phys. Lett. 63, 2961 (1993); http://dx.doi.org/10.1063/1.110286 (3 pages) | Cited 41 times

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Superconducting tunnel junctions coupled to superconducting absorbers may be used as high‐resolution, high‐efficiency x‐ray spectrometers. We have tested devices with niobium x‐ray absorbing layers coupled to aluminum layers that serve as quasiparticle traps. The energy resolution at 6 keV was 49 eV full width at half‐maximum. We estimate that each quasiparticle tunnels an average of 19 times before recombining, increasing the total charge transferred and therefore decreasing the effects of electronic noise.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
29.40.Wk Solid-state detectors
74.78.Fk Multilayers, superlattices, heterostructures

Growth of superconducting Y‐Ba‐Cu‐O films on spinel and garnet

Siu‐Wai Chan, Manoj Chopra, Cheng‐Chung Chi, Tony Frey, and Chang C. Tsuei

Appl. Phys. Lett. 63, 2964 (1993); http://dx.doi.org/10.1063/1.110287 (3 pages) | Cited 1 time

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Spinel and garnet single crystals of low dielectric constants and loss tangents have been investigated as possible substrate materials for the growth of the Y‐Ba‐Cu‐O superconducting films. In addition to their desirable dielectric properties, these materials are chemically compatible with silicon and compound semiconductors and can be used as the interface materials for the integration of cuprate superconducting films with semiconducting devices. The Y‐Ba‐Cu‐O films grown on (001) MgAl2O4 and (001) Y3Al5O12 from a co‐evaporation deposition with a subsequent wet anneal exhibit superconductivity with a transition temperature Tc(R=0) of 57 and 74 K, respectively, while strongly (001) textured YBa2Cu3O7−x films from the in situ laser deposition grown on (001) MgAl2O4 and (001) Y3Al5O12 show superconducting transition temperatures Tc(R=0) of 77 and 87 K, respectively. Our work demonstrates that these two materials are viable substrates for the Y‐Ba‐Cu‐O thin films in high frequency device applications.
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68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Surface study of a,b‐axis oriented YBa2Cu3O7−δ epitaxial thin films by in situ angle resolved x‐ray photoemission spectroscopy

N. Terada, S. Ishibashi, M. Jo, M. Hirabayashi, H. Ihara, and S. Yamamoto

Appl. Phys. Lett. 63, 2967 (1993); http://dx.doi.org/10.1063/1.110288 (3 pages) | Cited 3 times

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In situ angle resolved x‐ray photoemission spectroscopy has been performed on superconducting a,b‐axis oriented YBa2Cu3O7−δ epitaxial films. The relative intensities of the Cu 2p Ba 3d, and Y 3d core emissions have shown the diffraction‐like dependence on the electron escape angle due to the spatial distribution of elements in the surface layer. The calculated results by the single scattering cluster model on the surface with the Cu‐O outermost layer show a better agreement with the experiment than the (Y, Ba)‐O in the outermost layer.
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74.78.-w Superconducting films and low-dimensional structures
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.-a Thin film structure and morphology

Transport properties of YBa2Cu3O7−δ/Y0.3Pr0.7Ba2Cu3O7−δ/YBa2Cu3 O7−δ Josephson junctions

C Stölzel, M. Siegel, G. Adrian, C. Krimmer, J. Söllner, W. Wilkens, G. Schulz, and H. Adrian

Appl. Phys. Lett. 63, 2970 (1993); http://dx.doi.org/10.1063/1.110289 (3 pages) | Cited 15 times

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YBa2Cu3O7−δ/Y0.3Pr0.7Ba2Cu3O7−δ /YBa2Cu3O7−δ Josephson junctions have been prepared by a multistep laser ablation process using an improved shadow mask technique. Junctions with barrier layer thicknesses larger than 12 nm exhibit current‐voltage characteristics which are close to those predicted by the resistively shunted junction (RSJ) model. Under microwave irradiation, clear Shapiro steps, which could be well described by the RSJ model, occur in the current‐voltage curves. From the exponential decrease of the critical current density with increasing barrier layer thickness, an order parameter decay length ξn of 21±4 nm at T=4.2 K has been determined for Y0.3Pr0.7Ba2Cu3O7−δ. The increase of the junction resistance with decreasing temperature indicates that the barrier layer dominates the junction properties.
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74.78.Fk Multilayers, superlattices, heterostructures
74.78.-w Superconducting films and low-dimensional structures
74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
85.25.Cp Josephson devices
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